Surviving desert extremes in the Kalahari

Posted by Hannelie Van As on 18 March 2013

While some people retreated into hiding places lined with tinned food and bottled water, I sat at Twee Rivieren in Kgalagadi Transfrontier Park on 31 December 1999. I watched thunderclouds roll in and lightning brighten the night sky; a bat-eared fox sat very close to me, as if mesmerised by the spectacle too.

1 January arrived like any other day – nature doesn’t keep track of dates or doomsday predictions – and it was another hot, hot day in this semi-arid region where rainfall is irregular, coming in the form of storms like the one I’d experienced.

My fascination with the place started during this first visit, so when the opportunity came to attend an orientation course on the park with SanParks Honorary Rangers, I jumped at it. Ranger and presenter Willie Engelbrecht grew up in the Kalahari; there could hardly be a better, more passionate tutor.

‘Temperatures drop to as low as -11° and climb as high as 42° Celsius. This, coupled with very little water, makes it a case of adapt or die for the fauna and flora living here,’ he said.

Most life forms are physiologically and behaviourally primed to regulate the ratio between water intake and loss. Animals stick to the unspoken rule of tolerance and avoidance (that is, if you can’t handle it, avoid it altogether) by moving during the early morning and late afternoon or staying below the surface. Indigenous herbivores such as springbok get much of the water they need from what they eat (a chemical reaction occurs when carbs are broken down, resulting in the release of carbon dioxide and water). Some animals dig up moisture-bearing bulbs and roots to get hydration; others migrate to areas with more food and water when necessary.

Ungulates such as gemsbok have developed a way of fooling their bodies into believing it’s cooler than it actually is. Their carotid rete system cools hot arterial blood by evaporation from moist surfaces in the nasal passages; when this blood circulates to the brain, it’s registered as cooler, allowing the body to continue functioning.

Most indigenous animals here (such as springbok) have white bellies to reflect the heat on the ground, keeping them cooler. Some species produce urine with high urea concentrations and faeces which is almost completely dry), preserving every bit of moisture.

But perhaps plants are the real heroes: some grasses have adapted by producing four carbon sugars instead of the usual three, making it possible for them to photosynthesise in temperatures above 30° Celsius.

The roots of the camelthorn tree can reach water up to 60 metres underground and the gemsbok cucumber can store about half a litre of water, but the winner has to be the marama bean. Also called the gemsbokboontjie, it’s not very impressive looking above ground – it grows like a common ground cover – but it has a hidden secret. Its bulb can weigh up to 250 kilograms and hold up to 60 litres of water!

It’s a veritable gold mine for thirsty animals, especially a rodent that can’t drink. The teeth of the Damara mole-rat make drinking pretty much impossible, so it relies on moisture in roots and bulbs found on its travels underground.

You have to marvel at the sheer magic of an ecosystem like this, surviving against the odds. I’ll just have to stop complaining about Johannesburg (I have all the food and water I need) and apply the rule to the irritating things such as traffic: tolerate or avoid.

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